Pesticide Residues in the Environment - Pesticides: Evaluation of Environmental Pollution - page 149

modelsandthecorrespondingcomputersimulationprogramsweredescribedbyLarson
etal.(1997),Azevedo(1998),Reichmanetal.(2000),Chenetal.(2001),andLietal.(2001).
Thedegradationandfragmentationofpesticidescanbedescribedbydifferenttransport
models.

• CREAMS(Knisel1980)
• AGNPS(Youngetal.1986)
• RZWQM(USDA-ARS1995).

Themodelsofpesticidetransportinsoilare

• SWACRO(Belmansetal.1983)
• MACRO(Jarvis1991)
• LEACHP(HutsonandWagenet1992)
• PRZM-2(Mullinsetal.1993).

The advantage of these models is the possibility of application to many pesticides,
though generally within limited spatial and temporal windows. Mathematical models
thatsimulatethefateofpesticidesintheenvironmentareusedfordevelopingtheenvi-
ronmentalestimatedconcentrations(EECs)orpredictedenvironmentalconcentrations
(PECs) (Wania 1998). The generic estimated environmental concentration (GENEEC)
model,developedbytheU.S.EnvironmentalProtectionAgency(EPA),determinesthe
genericEECforaquaticenvironmentsunderworst-caseconditions(Wania1998).Such
models are the pesticide root zone model (PRZM), edge of ield runoff/leaching the
exposureanalysismodelingsystem(EXAMS),fateinsurfacewaters,andAgDrift(spray
drift)(Wania1998;Whitford2002)thatappliesadditionalparameters,moredescriptive
ofthesitestudies(Wania1998).PRZMsimulatestheleaching,runoff,anderosionfrom
an agricultural ield and EXAMS simulates the fate in a receiving water body (Wania
1998).
Thedevelopmentofgeographicinformationsystem(GIS)technologyandremotesens-
ingoffersperspectivesfortheimminentevolutionofcomprehensivepesticidetransport
models.Asoneoftheirst,thescreeningmodel,attenuationfactor(AF)(Equations6.1and
6.2)developedin1985byRaoetal.(1985),servesasanindexforpesticidemassemission
fromthevadosezoneandisdeinedas

(6.1)

M
M

− 0 693 × × L RF FC

q t

×

1

AF = = exp

×

0 1 2

BD OC K
FC

× × AC K

FC

×

(6.2)

oc H

RF = 1 + +

whereM 0 istheamountofpesticideappliedatthesoilsurface;M 1 ,theamountofpesti-
cideleachingtogroundwater;RFtheretardationfactor,whichrepresentstheretardation